For astrophotography there are nice clip-in filters to be placed in the bayonet mouth of the camera. For APS-C bodies they have been available for years but since recently for FF bodies.
http://www.astronomik.com/en/clip-fi...ollformat.html
These filters can be installed for astrophotos only so it is easy to install and can be uninstalled easily when doing ordinary photography as often the user wishes. (Un)installation does not require any tools.
The problem is however, that the user should enable mirror lockup to install this filter and after installation of the filter the mirror keeps locked up as long the filter in installed. No problem for AP as one (in my case a DSLR controller equipped Android tablet) focus exactly with Liveview at 10x magnification. But, according to the supplier, the filter *prevents* the mirror popping down after taking a photo. So I am reluctant to buy such filters despite their excellent quality, use with *any* lens (or telescope) and ease to (un)install.
Will this damage the mirror box mechanism ?